Thixotropic compositions



Patented Mar. 30,1954

THIXOTROPIC COMPOSITIONS Franklin Veatch, Cleveland, and Ellis C.Persing, Jr.,. Shaker Heights, Ohio, assignors to The Standard OilCompany, Cleveland, Ohio, a corporation of Ohio No Drawing. ApplicationDecember-14,1948, Serial No. 65,288

Claims.

This invention relates to thixotropic oil compositions comprising an oiland a hard wax-like material, more particularly, fully hydrogenatedcastor oil; which composition, may or may not, have certain solidsincorporated therein.

Before discussing the nature of the above composition, its advantagesand uses, together with illustrative examples, it is deemed desirable todefine certain terms to be used herein, in order that the scope andmeaning of the invention may be fully understood as it is furtherdescribed.

The reference to oil base as used herein, refers to oils of both mineralas well as animal and vegetable origin, and includes any unctuoussubstance which is liquid. The mineral oils may be derived frompetroleum or coal tar, for example, and may occur naturally or be madesynthetically by polymerization of olefins, alkylation condensations,etc. They may vary in viscosity from 50 to 75 S. U. S. at 100 F. such asare characteristic of torch oils .and the light household oils upthrough the oils having a viscosity of 4500 S. U. S. at 100 F. which arecharacteristic of certain bright stocks. (All viscosities herein are at100 F. unless otherwise stated.) They include, for instance, raw oilssuch as waxy oils, and oils refined by various methods, such asdewaxing, acid treating or solvent refining, including the highlyrefined white medicinal oils.

As illustrative of the animal and vegetable oils are ordinary castoroil, lard oil, neats-foot oil, olive oil, cocoanut oil, palm oil,soybean oil, cottonseed oil, and any of the. other naturally occurringoils which are liquid at ambient temperature, as well as equivalentsformed synthetically. These oils may be or include large amounts offatty acids, mcno-glycerides, etc.

Included also within the above definition are oils which have beenreacted with or have dissolyed therein elements or compounds formodifying their characteristics, more particularly oils haying extremepressure (E. P.) properties, and industrial oils such as cutting andgrinding oils. These may, for example, have sulfur or sulfur compounds,phosphorus or phosphorus compounds, phosphorus sulfides, chlorine orchlorinecontaining compounds dissolved therein or reacted therewith. Theoil base may contain compounds or reaction products which have beenadded thereto as a so-called additive forthe purpose of rendering theoil resistant to oxidation, to inhibit rusting, to improve resistance tocorrosion, imparting E. P. properties, or other modifications."'Alternatively the additive may be added separately'and therefore, maynot be regarded as an element of the oil base in the sense that it ispresent in the oil base when the hardened castor oil is dispersedtherein.

The combination of the oil and the fully hydrogenated castor oil is aphysical mixture and it is not believed to involve any chemical reactionbetween the components. The novel properties are thought to result fromthe particular physical association of the two components. For thisreason the wide variations in chemical compositions of the oils do notaffect the results obtained.

The other essential component. is a hard waxlike material which isprimarily or consists essentially of l2-hydroxystearin (glycerylhydroxystearate) which may be formed by the hydrogenation of castor oilto a low iodine value, i. e., fully hydrogenated. While this. materialmay be more closely related to a fat than toa wax in chemicalcomposition, it possesses many wax-like properties; more particularly,it has a relatively high solidification point of 86 to 88? C. (187- 190F.). It is to be distinguished from most hydrogenated vegetable oranimal oils since few can be hydrogenated to have a melting point muchabove C. It is extremely hard, pearl white in color, and practicallyodorless. It has an acid number of. 2.0,. a saponification value of 1'75to 185, an iodine number of 2.5 to 8.5, and an hydroxyl number of to165. It is extremely insoluble, and none of the common solventsdissolved as much as 2%. It is available under the trade name Opalwax,and will be referred to hereinafter as fully hydrogenated castor oil.

Compositions made by combining the oil with the fully hydrogenatedcastor oil according to the methods to be described hereinafter possessthixotropic properties. Thixotropy hos been extensively investigated asone aspect of rheology. It is a property possessed by a composition ofbeing liquid under conditions of agitation and of being solid orgel-like when quiescent. Thixotropic compositions may also be defined asundergoing reversible liquid-gel transitions. A thixotropic compositionis to be distinguished from one which hardens through cooling. such asparaffin wax and which may be applied to a surface in a hot liquid formto harden upon cooling. A characteristic of a thixotropic composition isthat the conversion from a solid or gel-like state to a liquid (and backagain), is not dependent upon a change of temperature, but rather isdependent on the stresses applied to the gel, firstly to initiate thetransition from the gelto the liquidstate and then maintain thecomposition in the-liquid state.

Thixotropic ,oil compositions are!" normally solid, in that they do notflow under the conditions of stress normally imposed upon them in use,and are to be distinguished from greases, since the latter term isrestricted to oils which have been thickened with a soap. Thecompositions of this invention, sincethey do not rely upon soap as athickening agent, are, therefore,

to be distinguished from greases, at least in so far as the mode ofobtaining a solid consistency, is concerned.

Thixotropic oil compositions have 'a' number of uses. For instance, inthe coating of metals to prevent rusting it is desirable to'spray orbrush an oil on a vertical metal surface while the oil is liquid underthe conditions of agitation incident to brushing or spraying, and thenhave the oil gel and become solid as soon as quiescent so is beingshipped to the final fabricators of commercial articles. They areordinarily applied to themetal surfaces with a brush and after standing,in some instances for only a few hours and in other cases after somemonths, cracks appear in the oil coating film, a phenomena known assplitting. The cracks or splits expose the metal at these points andrust protection is considerably decreased. It is characteristic of theas to remain fixed on the surface and not run ofi. Other applicationswill be immediately apparent, such as the coating of metal parts'duringsteps of manufacture to prevent rusting, coating of farm implements toprevent rust and other deterioration, and any other uses in which an oilcoating to protect the material coated is desirable.

Another use of such a composition is in connection with a cutting oil. Aplumber, for example, when cutting threads on a pipe, generally appliesa cutting oil to the pipe or the die,'and as an excess is usually usedthe excess drips on the floor. If this operation is being carried out inthe household, and such threading operations are commonly done on thepremises. where plumbing is being'installed, the objections are at onceapparent. A thixotropic cutting oil on the other hand, by means of asuitable pump type dispenser, can be ejected as a liquid on the work oron the die, and then set up to a gellike condition as soon as itisquiescent on the work, so as not to drip off on the floor. Another useof a thixotropic composition is as a substitute for greases, where thelubrication must adhere to the surface and not run off. Examples are diecasting and forge die lubricants, slide and way lubricants, and otherthickened lubricants. I t

Other uses include ointment bases to provide an ointment which can berendered liquid while being rubbed on the skin, and then set to a solidwhen quiescent. This is a particularly advantageous use since thetemperature of theskin is usually higher than the ambient temperature ofthe ointment, and except for any thixotropic properties, an ointmentwould tend to be more liquid on the skin than in the jar.

In any of the compositions contemplated herein for any uses, there maybe included any compatible material as long as it does not destroy thethixotropic properties. For example, an amount of solids such asgraphite, mica asbestos fibers, lamp black, aluminum' powder andpigments may be included. In an ointment base any drum, perfume,coloring material may be included. The expression consisting essentiallyof is used to define the components essential for the thixotropicproperties and does not exclude other components as long as they do notvitiate the purpose of the invention.

The invention will be described in connection with the followingembodiments, but which are not to be construed as limitations on theinvention of the scope described and. hereinafter covered in the claims.

slushing oils.--The invention is well illu a d "Petrolatum type slushingoils. Adjustment of the viscosity of the oil and the relativeproportions of ingredients does not cure splitting and at best onlyalters the* time that it takes to develop.- In accordance with theinvention a thixotropic slushing oil composition can be made which notonly may be applied in relatively liquid form by brushing so as togreatly facilitate the application, but which gels quickly afterstanding and which is free from or has a minimum of the splitting actionreferred to. The following composition is illustrative:

, Per cent Straw paraffin oil 97.5 Fully hydrogenated castor oil 2.5

. stirring or shaking it may be poured from the bottle as a liquid, andafter again standing it assumes its jelly-like form. It is suitable foruse as a slushing oil or for any other coating purpose and issubstantially free from splitting.

EXAMPLE II I Per cent No. 300 red oil 92.5 Oronite sulfonate 5 Fullyhydrogenated castor oil 2.5

No. 300 red oil is a Mid-Continent acid-refined oil having a, viscosityof 300 S. U. S. The Orcnite sulfonate is an alkyl aryl sodium sulfonateand may be replaced by any of the petroleum. sulfonates which are wellknown as a class in this art for imparting anti-rust properties to acomposition. The composition is useful as a slushing oil and as a rustinhibitor. It is free from splitting and has thixotropic properties.This composition also has the unusual and dc:- sirable property ofsetting up even more firmly when steel surfaces coated therewith areheated to temperatures as high as F. as might occur in direct summersunlight.

EXAMPLE III The oil and the sulfonate have been described in theprevious example. In this example. as cornparedigwith. Example II, theamount-of fully hydrogenated castor oil, has been reduced in half and asubstantial amountof petrolatum is em- 5 ployed, an ingredient commonlyused in prior art slushin'g oils. Nevertheless this use of the smallamount of fully hydrogenated castor oil imparts satisfactory'thixotropic properties to the composition and markedly minimizes orelimi nates splitting.

EXAMPLE IV Per cent No. 225 red oil 97.5 Fully hydrogenated castor .oil2.5

No. 225 red oil is similar to the :oil in Examples II and III exceptthat it has .a viscosity of 225 S. U. S. This composition is asemi-solid lubricant with a consistency of soft grease. It issuitablefor the protection-of tools and metal equipment against weatherconditions and in some instances as a slushing oil. It is also useful inplaces where a very soft grease is desired. A comparison of this examplewith Example I will show that the composition is similar except for thegreater viscosityof the oilbase and thegreater consistency in thismixture.

EXAMPLE V Percent Zone paraflin oil 99.5 Fully hydrogenated castor oil0.5

Zone parafiin oil is an acid-refined oil having aviscosity of 150 S. U.S. The composition is a slightly gel-like oil with definite thixotropicflow characteristics and is suitable as a slide and way lubricant.Comparison with Examples I and IV will show that the oil base isintermediate in viscosity but the amount of fully hydrogenated castoroil is much less accounting for the less pronounced gel-likecharacteristics.

EXAMPLE VI Per cent Solvent extracted lubricating oil S. A. E. 30 97 .5Fully hydrogenated castor oil 2.5

EXAMPLE VII Per-cent Polarine No. 50;. l 07.5 Fully hydrogenated castoroil 2.5

Polarine No. '50 is a commercial lubricating oil having a viscosity of1000 S. U. S. (S. A. E..No.;.50).

The composition is a semi -solid composition'of a consistency of softgrease and useful as a lubricant where greases are used.

EXAMPLE VIII Per cent Pennsylvania bright stock 99 Fully hydrogenatedcastor oil-.- I 1 Pennsylvania bright stock has a viscosity of 12200 S.U. S. This composition is similar to the com position in Example V, butmore viscous and showing more pronounced thixotropic gel-like 1properties, it is useful-as'a' slide and way lubricant. A furthercomparison of this example with Example shows that the viscosity 0: thel is much greater, and the amount of fully hydra genated castor oil islarger. accounting for'the EXAMPLE X Per cent Commercial cutting oil No.l 97 Fully hydrogenated castor oil 3 2;"

more viscous and more pronounced thixotropic properties.

EXAMPLE IX Percent Wax slops a 97 Fully .hydrogenate' castor oil 3 Waxslops .is ..a lubricating oil fraction containing microcrystalline andparafiin wax which is dif ficult to separateirom the oil and ordinarilylittle attempt is made to process it because of the dif- .ficulty ofseparating the wax. This oil base in some respects may be likened to anoil containing petrolatum and parailin wax dissolved there- Iihecomposition is an adhesive gelatinous semi-solid which becomes liquid onagitation and is applicable to surfaces with a spray type applicator. Itis suitable as .a rust inhibitor for application to the undersurfaces ofautomobiles and as achromium plated surface preserver.

P The cutting oil in this example is available on the market and is alubricating oil of medium viscosity mixed with 20% lard oil andcontaining 1 of added reacted sulfur. The composition is an adhesivesemi-solid lubricant having the v consistency of very soft grease andreadily applicable by a pump type squirt can. It is useful as a cutting.oil particularlyior hand :tools which requireno-drip characteristics. i

Per cent Commercial cuttingzoil No. 2 95 Fully hydrogenated castor oil 5The cutting oil in this example is available on the market and is amedium viscosity lubricating 011 containing 2% of added reacted :sulfurand 1 /2% chlorine in the form :of .a chlorinated wax. The compositionis similar in characteristics to Example VIII but slightly more firmbecause of the larger amount of the fully hydrogenated castor oil. It issuitable .for the same purposes.

EXAMPLE. XII

Per cent Commercial cutting oil .No. 1, 97% -1 90 Fully hydrogenatedcastor oil, 3% ml Sulfur 10 The wax slops are described-in connectionwith Example IX. The composition is a silver lustre colored gel-likematerial applicable in the same way as the composition of Example .IXand is a rust inhibitor for the rusted undersurfaces of automobiles.

EXAMPLE XIV Percent Wax slops, -97% l.'.-' ...L Fully hydrogenatedcastoroil. =3=%-- Asbestos fiber 30 The wax slops are defined inconnection with Example IX. The composition is a matted gelatinoussemi-solid with exceptionally good adhesive properties suitable as anundercoating of automobiles. to check rusting.

EXANIPLE' XV Per cent Torch oil, 97.25% 80 Fully hydrogenated castoroil, 2.75% Powdered mica- 20 Torch oil is a gas, oil having a viscosityof 50 S. U. S. The composition is a semi-fluid oil with. definitethixotropic properties in which mica is permanently suspended. It issuitable as a die casting lubricant for zinc and lead where evensuspension of the particles is desirable.

EXAMPLE XVI Per cent No. 1 bright sto 94 Fully hydrogenated castor oil 1Powdered graphite 5 The No. l bright stock'is a Mid-Continent brightstock having a viscosity of 4300 S. U. S; The composition is a fairlyfluid oil but having thixotropic properties, and having graphitepermanently suspended therein. It is applicable with a brush andsuitable as a forge die lubricant.

EXAMPLE XVII Per cent Ordinary castoroil 95 Fully hydrogenated castoroil 5- The composition is a semi-solid translucent material having agrease-like consistency with pronounced thixotropic properties and issuitable as an ointment base or for lubricating applications in whichcastor oil is used.

Per cent Medium white oil 97.5 Fully hydrogenated castor oil 2.5

The medium white oil has a viscosity of 200-300 S. U. S. at 100 F. andis of the type suitable for medicinal use. The composition is a whitesemisolid thixotropic structure of grease-type consistency. It issuitable as an ointment base for instance, to which a sun filteringcompound can be added for making a sunburn protective cream. It is alsosuitable as a substitute for a soft grease in the food industry where agrease would be desirable such as in sealing cans, but which cannot nowemploy a' grease because of the taste which would be imparted to food bythe soap in thegrease.

Method of preparation g later or at the, same time th at the oil baseand I the fully hydrogenated castor oil are mixed.

The fully hydrogenated castor oilisnot soluble in the oil base under theusual temperature conditions of use and must be incorporated therewithso as to be in an extremely finely dispersed form, if the composition isto have the optimum thixotropic properties. The extent of the thixotropyamon ctherth nss. a junct n o nerti s z It isdesirablethat theparticlesizeof 211831 1 hydrogenated castor oil. in the oil base beextremely small (sub-microscopic) so that there is substantially nolight scattering or Tyndall efiect.

A preferred method of making the compositions is to melt the fullyhydrogenated castor oil in a portion-of the oil base at a temperatureabove the melting point of the fully hydrogenated castor oil, such as 95to 100 C. At this temperature it is soluble in the oil base. This hotsolution of the fully hydrogenated castor oil is then added to theremainder of the oil base with agitation so that the mixture assumes atemperature below the melting point of the fully hydrogenated castoroil. Additional chilling may be used. One such method is to feed astream of to parts of the oil base at room temperature or below and astreamof 50 to 10- parts of hot oil base containing the melted. fullyhydrogenated castor oil so that the two streams enter'a gear pump; Theintense agitation obtained as the two streams pass through the gear pumpand the cooling due to the relatively large stream of cooler oil baseresults in the requisite fine dispersion.

Another method may be used in which the fully hydrogenated castor oil ismelted in all of the oil base, and the entire solution rapidly chilledwith agitation, such as can be done with a turbomixer. It will beunderstood that other equivalent methods may be used in which rapidchilling,

preferably with agitation, so as to obtain the requisite small particlesize.

In order to determine and compare the thixotropic properties of thecomposition of the invention with those of the prior art a test wasdeveloped which measured the static forces in fundamental units. Priorstudies of thixotropic compositions have been made primarily withvarious types of viscosimeters which deal with the dynamic behavior rofthe compositions during or after transition from the gel to the liquidphase. The test developed, however, measures the time and the stressesrequired to initiate the transition from the gel to the liquid phase.This initiation of the breakdown may be regarded as the static yieldvalue. This is the important value with which to appraise the usefulnessof a thixotropic composition. For example, after a thixotropic slushingoil has been applied to the surface of a machine and gelled, whatforces, such as shock or jar, will cause the gel to liquefy so thatit-Would move on or from the surface? In accordance with this test aplate of definite area in square centimeters is immersed in thethixotropic composition to be tested and connected to a left-hand sideof a balance, and the right-hand side is weighted to balance so that noforce is exerted on the plate when immersed in the thixotropiccomposition. A sample of the thixotropic composition is. placed in abeaker and allowed to .stand at least'one hour .to reset. The plate isimmersed so asto minimize and equalize any gel breakdown over theimmersed area of the plate. Weights are thenapplied to the righthandside of the balance to such an extent and such a. rate that the plate onthe left-hand side of the balanceislifted from thethixotropiccomposition 1 mm. in 10 seconds.. .The static yield stresses in, dynesper square centimeter can be readilyd'eteriniried because theimmer'sedarea of the plate is in square'centimeters and the force in a given timeis readily. converted to dynes.

Measurementsshow that the yield forces are a linear function-of the areaof the plate immersed and. tha t e eis o ne si 2. o cc Applying thistest to a composition made up of No. 300 red oilan. acid treated oil oraviscosity of 300 S. U. S. with various amounts of fully hydrogenatedcastor oil (in accordance with the invention) and petrolatum inaccordance with the prior art) gave the following: results.

Plotting the percent gelling agent against the logarithmof the yield'sg-ress shows that the petrolatum-containing composition. gives almost astraight line relationship. However it shows that there is a thresholdrequirement of about 15% petrolatum. When less than this is used themixtures are non-thixotropic. It' alsoindicates that the amount of theyield stress obtainable is not very high even when exceptionally largeamounts of the petrolatum are used.

n the other hand the compositions containing the fully hydrogenatedcastor oil pass through the zero point, indicating that even extremelysmall amounts of the fully hydrogenated castor oil impart aproportionate degree of thixotropy. The slope of the curve is such as toshow that extremely high static yield values can be obtained withoutresorting to large amounts of the fully hydrogenated castor oil.

It has also been observed that some prior art thixotropic compositionstend to creep, that is, they yield after a certainlength of time duringwhich stress is applied, even though they do not yield immediately, sayin 10 seconds after the stress is applied. In order to evaluate thisproperty, compositions containing fully hydrogenated castor oil andpetrolatum in amounts to give similar viscosities of a Brookfieldviscosimeter were compared. The results are shown in the followingtable:

Brookfleld Viscosity Yield Gelling Agent Stress in ime in 30 Minutedynes/cm 2 Minutes Initial 2.5% Fullv hydrogenated Castor Oil. 16, 6004, 700 30 3, 000.0 30% Petrolatum 12, 200 6, 300 24 1.0 Do 12, 200 6,300 34 0. 83

From this it will be seen that when hardened castor oil is employed inthe small amount of 2 /2% as compared with 30% petrolatum and upon theapplication of equal yield stress, the time for creep is almostinfinitely greater in the case of a composition made in accordance withthe invention.

I am aware that it has been proposed hereinbefore to make a thixotropiclubricating jelly by the mixing of a high viscosity index oil, such asan oil having a 95 V. I. with a relatively large proportion of anamorphous wax alone or with other waxes such as crude montan wax. Theseare made by mixing at a high temperature and merely allowing the mixtureto cool. For instance, about 61 parts of the 95 V. I. oil, 20.1 parts ofamorphous wax (155 F., M. P.) and 1 to 5 parts of crude montan (170 F.,M. P.) are heated until fluid and allowed to cool. According to. thisprior art,. crude montan wax alone will not form thixotropic jellieswith this oil, and while refined montan wax alone with this oil willform. a thixotropic jelly, '10. parts of the refined montan wax arerequired. In contrast with this state. of the prior art, my inventiondoes not require the use of. a high V. I. oil and requires muchsmalleramounts of the fully hydrogenated castor oiltofobtain, excellentthixotropy. Furthermore, the method by which my compositions are madealso shows the unique properties of fully hydrogenated castor oil inthis regard, since my compositions, if made by the prior art processesreferredto would not contain the fully hydrogenated castor oil in suchsmall particles as to have the optimum thixotropic properties.

The amount of 'the fully hydrogenated castor oil' required in accordancewith my invention is generally not over 5% to obtain a semi-solidcomposition of grease-like texture and in most instances amounts of theorder of 1 to 3% are satisfactory in accordance with my inventionto-obtain definite thixotropic properties.

While I have described my invention with reference to fully hydrogenatedcastor oil as the best mode of achieving the desirable results, I do notintend to exclude equivalent materials or other modifications orvariations within the following claims.

We claim:

1. A thixotropic oil having a gel-like to solid consistency whenquiescent and fluid properties under conditions of agitation, consistingessentially of fully hydrogenated castor oil dispersed as solidparticles of submicroscopic size inv a liquid oil base, saidhydrogenated castor oil being present in an amount to impart thixotropyto the oil, but not over 5% by weight of the composition.

2. A thixotropic oil in accordance with claim 1 in which the oil is amineral oil of lubricating viscosity.

3. A thixotropic oil in accordance with claim 1 in which thehydrogenated castor oil is present in an amount within the range from0.5 to 5%.

4. A thixotropic oil in accordance with claim 1 which contains a rustinhibitor.

5. A thixotropic oil in accordance with claim 1 having a compatiblefinely-divided solid suspended therein.

6. A thixotropic oil in accordance with claim 1 having graphitesuspended therein. 7. A thixotropic slushing oil having a gel-like tosolid consistency when quiescent and fluid properties under conditionsof agitation, consisting essentially of fully hydrogenated castor oildispersed as solid particles of submioroscopic size in a liquid mineraloil base of a viscosity of 75 to 3000 S. U. S. at F., and containing 1%to 10% of a petroleum sulfonate rust inhibitor, said hydrogenated castoroil being present in an amount to impart thixotropy to the oil, but notover 5% by weight of the composition.

8. A method of making a thixotropic oil composition which comprisesheating solid fully hydrogenated castor oil in a liquid oil base to atemperature above the melting point of the fully hydrogenated castor oilto dissolve the same in the oil base, and cooling said heated mixture toa temperature below the melting point of the fully hydrogenated castoroil to disperse the same in the oil base as solid particles ofsubaovasse microscopic size, said hydrogenated castor oil being in anamount not over to impart a gel-like to solid thixotropic consistency tosaid composition when quiescent and fluid properties under conditions ofagitation.

" 9. A method of making a thixotropic oil composition which comprisesheating solid fully hydrogenated castor oil in a liquid oil base to atemperature above the melting point of the fully hydrogenated castor oilto dissolve the same in the oil base, and quickly cooling said heatedmixture with agitationto a temperature below the melting point of thefully hydrogenated castor oil todisperse the same in the oil base assolid particles of submicroscopic size, said hydrogenated castor oilbeing in an amount not over 5% to impart a gel-like to solid thixotropicconsistency to said composition when quiescent and fluid propertiesunder conditions of agitation.

10. A method of making a thixotropic oil composition which comprisesheating solid fully hydrogenated castor oil in a liquid oil base to atemperature above the melting point of the fully hydrogenated castor oilto dissolve the same in the oil base, and quickly cooling said heatedmixture by mixing the same with an additional amount of said oil base ata lower temperature to reduce the mixture with agitation to atemperature below the'melting point of the fully hydrogenated castor oilto disperse the same in the oil base as solid particles ofsubmicroscopic size, said hydrogenated castor oil being in an amount notover 5% to impart a gel-like to solid thixotropic consistency to saidcomposition when quiescent and fluid properties under conditions ofagitation.

FRANKLIN VEATCI-I.

ELLIS C. PERSING, JR.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,457,169 Howe et a1. May 29, 1923 1,617,077 Nill et al. "Feb.8, 1927 1,795,993 Bransky Mar. 10, 1931 2,356,863 McLaren et a1. Aug.29, 1944 2,412,634 Schwartz Dec. 17, 1946 2,447,506 Jubanowsky Aug. 24,1948 2,493,483 Francis et a1. Jan. 3, 1950 2,537,629 Brown Jan. 9, 1951FOREIGN PATENTS Number Country Date 576,089 Great Britain Mar. 19, 1946

1. A THIXOTROPIC OIL HAVING A GEL-LIKE TO SOLID CONSISTENCY WHENQUIESCENT AND FLUID PROPERTIES UNDER CONDITIONS OF AGITATION, CONSISTINGESSENTIALLY OF FULLY HYDROGENATED CASTOR OIL DISPERSED AS SOLIDPARTICLES OF SUBMICROSCOPIC SIZE IN A LIQUID OIL BASE, SAID HYDROGENATEDCASTOR OIL BEING PRESENT IN AN AMOUNT TO IMPART THIXOTROPY TO THE OIL,BUT NOT OVER 5% BY WEIGHT OF THE COMPOSITION.
 8. A METHOD OF MAKING ATHIOXTROPIC OIL COMPOSITION WHICH COMPRISES HEATING SOLID FULLYHYDROGENATED CASTOR OIL IN A LIQUID OIL BASE TO A TEMPERATURE ABOVE THEMELTING POINT OF THE FULLY HYDROGENATED CASTOR OIL TO DISSOLVBE THE SAMEIN THE OIL BASE, AND COOLING SAID HEATED MIXTURE TO A TEMPERATURE BELOWTHE CASTOR OIL TO DISPERSE THE FULLY HYDROGENATED CASTOR OIL TO DISPERSETHE SAME IN THE OIL BASE AS SOLID PARTICLES OF SUBMICROSCOPIC SIZE, SAIDHYDROGENATED CASTOR OIL BEING IN AN AMOUNT NOT OVER 5% TO IMPART AGEL-LIKE TO SOLID THIXOTROPIC CONSISTENCY TO SAID COMPOSITION WHENQUIESCENT AND FLUID PROPERTIES UNDER CONDITIONS OF AGITATION.